P
US9804371B2ActiveUtilityPatentIndex 42

Zoom lens and image pickup apparatus including the same

Assignee: CANON KKPriority: Aug 10, 2015Filed: Jul 25, 2016Granted: Oct 31, 2017
Est. expiryAug 10, 2035(~9.1 yrs left)· nominal 20-yr term from priority
Inventors:SHINOHARA KENJI
G02B 13/009G02B 15/20G02B 27/0025G02B 15/177G02B 15/143507
42
PatentIndex Score
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Cited by
7
References
11
Claims

Abstract

A zoom lens according to the present invention includes, in order from an object side to an image side: a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; and a third lens unit having a positive refractive power, in which a distance between adjacent lens units varies during zooming, the configuration of the second lens unit, the curvature radius Rb 2 obj of a lens surface of a cemented lens GRb 2 on the object side included in the second lens unit, the curvature radius Rb 2 img of a lens surface of the cemented lens GRb 2 on the image side, the focal length f2 b img of the cemented lens GRb 2, and the focal length f 2 of the second lens unit are appropriately set.

Claims

exact text as granted — not AI-modified
What is claimed is: 
     
       1. A zoom lens comprising, in order from an object side to an image side: a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; and a third lens unit having a positive refractive power, a distance between the adjacent lens units varying during zooming,
 wherein the second lens unit includes a plurality of lenses, a cemented lens GRb 2  is disposed nearest to the image side in the second lens unit, and the cemented lens GRb 2  includes a negative lens and a positive lens cemented to the image side of the negative lens, and 
 provided that a lens surface of the cemented lens GRb 2  on the object side has a curvature radius Rb 2 obj, a lens surface of the cemented lens GRb 2  on the image side has a curvature radius of Rb 2 img, the cemented lens GRb 2  has a focal length f 2 bimg, and a focal length of the second lens unit is f 2 , following conditional expressions are satisfied,
   1.65<(Rb2obj+Rb2img)/(Rb2obj−Rb2img)<50.00,
 
   and 
   1.0 <f 2 b img/ f 2<10.0. 
 
 
     
     
       2. The zoom lens according to  claim 1 , wherein provided that a lens surface of the negative lens on the object side included in the cemented lens GRb 2  has a curvature radius Rb 2   n _obj and a lens surface of the negative lens on the image side has a curvature radius Rb 2   n _img, a following conditional expression is satisfied,
   −4.5<(Rb2 n _obj+Rb2 n _img)/(Rb2 n _obj−Rb2 n _img)<0.2.
 
 
     
     
       3. The zoom lens according to  claim 1 , wherein provided that an amount of movement of the second lens unit is M 2  during zooming from a wide angle end to a telephoto end, and an amount of movement of the third lens unit during zooming from the wide angle end to the telephoto end is M 3 , a following conditional expression is satisfied,
   −18.0 <M 2 /M 3<−7.0.
 
 
     
     
       4. The zoom lens according to  claim 1 , wherein provided that a focal length of the third lens unit is f 3 , a following conditional expression is satisfied,
   0.30 <f 2 /f 3<0.65. 
 
     
     
       5. The zoom lens according to  claim 1 , wherein the second lens unit includes, in order from the object side to the image side: a positive lens; a cemented lens GRa 2  including a positive lens and a negative lens cemented to each other; and a cemented lens GRb 2  including a negative lens and a positive lens cemented to each other. 
     
     
       6. The zoom lens according to  claim 5 , wherein provided that a lens surface of the negative lens on the object side included in the cemented lens GRa 2  has a curvature radius Ra 2   n _obj and a lens surface of this negative lens on the image side has a curvature radius Ra 2   n _img, a following conditional expression is satisfied,
   0.2<(Ra2 n _obj+Ra2 n _img)/(Ra2 n _obj−Ra2 n _img)<1.2.
 
 
     
     
       7. The zoom lens according to  claim 5 , wherein provided that a lens surface of the positive lens on the object side included in the cemented lens GRb 2  has a curvature radius Rb 2   p _obj, and a lens surface of this positive lens on the image side has a curvature radius Rb 2   p _img, a following expression is satisfied,
   0.01<(Rb2 p _obj+Rb2 p _img)/(Rb2 p _obj−Rb2 p _img)<2.50.
 
 
     
     
       8. The zoom lens according to  claim 5 , wherein provided that a lens surface of the cemented lens GRa 2  on the image side has a curvature radius Ra 2   n _img and a lens surface of the cemented lens GRb 2  on the object side has a curvature radius Rb 2   n _obj, a following expression is satisfied,
   −1.0<(Ra2 n _img+Rb2 n _obj)/(Ra2 n _img−Rb2 n _obj)<−0.3.
 
 
     
     
       9. The zoom lens according to  claim 1 , wherein provided that a negative lens G 1   n  is disposed nearest to the object side in the first lens unit, and a lens surface of the negative lens G 1   n  on the object side has a curvature radius RG 1 obj and a lens surface of the negative lens G 1   n  on the image side has a curvature radius RG 1 img, a following expression is satisfied,
   0.4<(RG1obj+RG1img)/(RG1obj−RG1img)<1.0.
 
 
     
     
       10. The zoom lens according to  claim 1 , wherein an effective image diameter at a wide angle end is smaller than an effective image diameter at a telephoto end. 
     
     
       11. An image pickup apparatus, comprising:
 a zoom lens; and 
 an image pickup element configured to receive an image formed by the zoom lens, 
 the zoom lens comprising, in order from an object side to an image side: a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; and a third lens unit having a positive refractive power, 
 wherein a distance between adjacent lens units varies during zooming, 
 the second lens unit includes a plurality of lenses, a cemented lens GRb 2  is disposed nearest to the image side in the second lens unit, and the cemented lens GRb 2  includes a negative lens and a positive lens cemented to the image side of the negative lens, and 
 provided that a lens surface of the cemented lens GRb 2  on the object side has a curvature radius Rb 2 obj, a lens surface of the cemented lens GRb 2  on the image side has a curvature radius of Rb 2 img, the cemented lens GRb 2  has a focal length f 2 bimg, and a focal length of the second lens unit is f 2 , following conditional expressions are satisfied,
   1.65<(Rb2obj+Rb2img)/(Rb2obj−Rb2img)<50.00,
 
   and 
   1.0 <f 2 b img/ f 2<10.0.

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